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Problem 7 EQ: How do geologists determine the actual age of rocks?

Problem 7 EQ: How do geologists determine the actual age of rocks?. They use radiometric dating!. The key to radiometric dating is the composition of igneous rocks. Igneous rocks composed of minerals Minerals composed of elements In nature, most elements have isotopes.

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Problem 7 EQ: How do geologists determine the actual age of rocks?

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  1. Problem 7 EQ: How do geologists determine the actual age of rocks? They use radiometric dating!

  2. The key to radiometric dating is the composition of igneous rocks Igneous rocks composed of minerals Minerals composed of elements In nature, most elements have isotopes

  3. Types of igneous rock deposits

  4. Radioactive Isotopes in Igneous Rocks Some isotopes are radioactive (nucleus gives off particles to reach stability) Elements have definite ratio of isotopes in a sample Radioactive isotopes (parent element) slowly decay to more stable form (daughter element) at constant rate Rate is called half-life

  5. How is radiometric dating performed? See Web Link Formula: t = 1.443 t1/2 ln(1+D/P) (ln=logex where e=2.718, t1/2=half-life)

  6. What does a parent half-life decay rate look like? See Decay Applet

  7. Most common Igneous Rock Half-lives

  8. Can you calculate the the age of the igneous rocks that have the following Pb-207 / U-235 (D/P) Ratios? RatioAge (my) 1 700 3 1400 7 2100 0.333 285 0.143 135 0.067 70

  9. The igneous rocks in this canyon were absolutely dated and the sedimentary rocks adjoining them can be relatively dated according to their position. Age-dating of Rocks Absolute and Relative

  10. Geologic History of OutcropAr-40/K-40 1.25 by Pb-207/U-235 0.7 by SS Sh Bentonite Ar/K: 0.143 Sh, marine fossils Basalt Pb/U: 0.143 SS Granite Pb/U: 1 Can you list the order of geologic events and their ages?

  11. THE END

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